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<pre><span class="sourceLineNo">001</span><a name="line.1"></a>
<span class="sourceLineNo">002</span>/*<a name="line.2"></a>
<span class="sourceLineNo">003</span> * Copyright (C) 2011 Archie L. Cobbs. All rights reserved.<a name="line.3"></a>
<span class="sourceLineNo">004</span> *<a name="line.4"></a>
<span class="sourceLineNo">005</span> * $Id: ByteArrayEncoder.html 689 2013-06-28 19:22:16Z archie.cobbs $<a name="line.5"></a>
<span class="sourceLineNo">006</span> */<a name="line.6"></a>
<span class="sourceLineNo">007</span><a name="line.7"></a>
<span class="sourceLineNo">008</span>package org.dellroad.stuff.string;<a name="line.8"></a>
<span class="sourceLineNo">009</span><a name="line.9"></a>
<span class="sourceLineNo">010</span>/**<a name="line.10"></a>
<span class="sourceLineNo">011</span> * Encodes {@code byte[]} arrays to and from hexadecimal strings.<a name="line.11"></a>
<span class="sourceLineNo">012</span> */<a name="line.12"></a>
<span class="sourceLineNo">013</span>public final class ByteArrayEncoder {<a name="line.13"></a>
<span class="sourceLineNo">014</span><a name="line.14"></a>
<span class="sourceLineNo">015</span>    private ByteArrayEncoder() {<a name="line.15"></a>
<span class="sourceLineNo">016</span>    }<a name="line.16"></a>
<span class="sourceLineNo">017</span><a name="line.17"></a>
<span class="sourceLineNo">018</span>    /**<a name="line.18"></a>
<span class="sourceLineNo">019</span>     * Encode a {@code byte[]} array as a {@link String}.<a name="line.19"></a>
<span class="sourceLineNo">020</span>     * Equivalent to:<a name="line.20"></a>
<span class="sourceLineNo">021</span>     * &lt;blockquote&gt;<a name="line.21"></a>
<span class="sourceLineNo">022</span>     * &lt;code&gt;encode(array, 0, array.length)&lt;/code&gt;<a name="line.22"></a>
<span class="sourceLineNo">023</span>     * &lt;/blockquote&gt;<a name="line.23"></a>
<span class="sourceLineNo">024</span>     *<a name="line.24"></a>
<span class="sourceLineNo">025</span>     * @param array byte array, or {@code null}<a name="line.25"></a>
<span class="sourceLineNo">026</span>     * @return hexadecimal string (or {@code null} if {@code array} was {@code null})<a name="line.26"></a>
<span class="sourceLineNo">027</span>     */<a name="line.27"></a>
<span class="sourceLineNo">028</span>    public static String encode(byte[] array) {<a name="line.28"></a>
<span class="sourceLineNo">029</span>        return encode(array, 0, array.length);<a name="line.29"></a>
<span class="sourceLineNo">030</span>    }<a name="line.30"></a>
<span class="sourceLineNo">031</span><a name="line.31"></a>
<span class="sourceLineNo">032</span>    /**<a name="line.32"></a>
<span class="sourceLineNo">033</span>     * Encode a {@code byte[]} array as a {@link String}.<a name="line.33"></a>
<span class="sourceLineNo">034</span>     *<a name="line.34"></a>
<span class="sourceLineNo">035</span>     * @param array byte array, or {@code null}<a name="line.35"></a>
<span class="sourceLineNo">036</span>     * @param off   offset into the array<a name="line.36"></a>
<span class="sourceLineNo">037</span>     * @param len   number of bytes to convert<a name="line.37"></a>
<span class="sourceLineNo">038</span>     * @return hexadecimal string (or {@code null} if {@code array} was {@code null})<a name="line.38"></a>
<span class="sourceLineNo">039</span>     * @throws IndexOutOfBoundsException if array bounds are exceeded<a name="line.39"></a>
<span class="sourceLineNo">040</span>     * @throws IllegalArgumentException  if {@code len} is greater than {@code Integer.MAX_VALUE / 2}<a name="line.40"></a>
<span class="sourceLineNo">041</span>     */<a name="line.41"></a>
<span class="sourceLineNo">042</span>    public static String encode(byte[] array, int off, int len) {<a name="line.42"></a>
<span class="sourceLineNo">043</span><a name="line.43"></a>
<span class="sourceLineNo">044</span>        // Check for null<a name="line.44"></a>
<span class="sourceLineNo">045</span>        if (array == null)<a name="line.45"></a>
<span class="sourceLineNo">046</span>            return null;<a name="line.46"></a>
<span class="sourceLineNo">047</span><a name="line.47"></a>
<span class="sourceLineNo">048</span>        // Check bounds<a name="line.48"></a>
<span class="sourceLineNo">049</span>        if (off &lt; 0 || len &lt; 0 || off + len &lt; 0 || off + len &gt; array.length)<a name="line.49"></a>
<span class="sourceLineNo">050</span>            throw new IndexOutOfBoundsException("array bounds exceeded");<a name="line.50"></a>
<span class="sourceLineNo">051</span><a name="line.51"></a>
<span class="sourceLineNo">052</span>        // Encode bytes<a name="line.52"></a>
<span class="sourceLineNo">053</span>        if (len &gt; Integer.MAX_VALUE / 2)<a name="line.53"></a>
<span class="sourceLineNo">054</span>            throw new IllegalArgumentException("array is too long");<a name="line.54"></a>
<span class="sourceLineNo">055</span>        char[] buf = new char[len * 2];<a name="line.55"></a>
<span class="sourceLineNo">056</span>        for (int i = 0; i &lt; len; i++) {<a name="line.56"></a>
<span class="sourceLineNo">057</span>            int value = array[off + i] &amp; 0xff;<a name="line.57"></a>
<span class="sourceLineNo">058</span>            buf[i * 2] = Character.forDigit(value &gt;&gt; 4, 16);<a name="line.58"></a>
<span class="sourceLineNo">059</span>            buf[i * 2 + 1] = Character.forDigit(value &amp; 0xf, 16);<a name="line.59"></a>
<span class="sourceLineNo">060</span>        }<a name="line.60"></a>
<span class="sourceLineNo">061</span><a name="line.61"></a>
<span class="sourceLineNo">062</span>        // Done<a name="line.62"></a>
<span class="sourceLineNo">063</span>        return new String(buf);<a name="line.63"></a>
<span class="sourceLineNo">064</span>    }<a name="line.64"></a>
<span class="sourceLineNo">065</span><a name="line.65"></a>
<span class="sourceLineNo">066</span>    /**<a name="line.66"></a>
<span class="sourceLineNo">067</span>     * Decode a {@link String} back into a {@code byte[]} array.<a name="line.67"></a>
<span class="sourceLineNo">068</span>     * Any extra whitespace in the string is ignored.<a name="line.68"></a>
<span class="sourceLineNo">069</span>     *<a name="line.69"></a>
<span class="sourceLineNo">070</span>     * @param text string previously encoded by {@link #encode}, or {@code null}<a name="line.70"></a>
<span class="sourceLineNo">071</span>     * @return original {@code byte[]} array (or {@code null} if {@code text} was {@code null})<a name="line.71"></a>
<span class="sourceLineNo">072</span>     * @throws IllegalArgumentException if any invalid non-whitespace characters are seen, or the number of hex digits is odd<a name="line.72"></a>
<span class="sourceLineNo">073</span>     */<a name="line.73"></a>
<span class="sourceLineNo">074</span>    public static byte[] decode(String text) {<a name="line.74"></a>
<span class="sourceLineNo">075</span><a name="line.75"></a>
<span class="sourceLineNo">076</span>        // Check for null<a name="line.76"></a>
<span class="sourceLineNo">077</span>        if (text == null)<a name="line.77"></a>
<span class="sourceLineNo">078</span>            return null;<a name="line.78"></a>
<span class="sourceLineNo">079</span><a name="line.79"></a>
<span class="sourceLineNo">080</span>        // Allocate array<a name="line.80"></a>
<span class="sourceLineNo">081</span>        byte[] array = new byte[text.length() / 2];<a name="line.81"></a>
<span class="sourceLineNo">082</span><a name="line.82"></a>
<span class="sourceLineNo">083</span>        // Parse bytes<a name="line.83"></a>
<span class="sourceLineNo">084</span>        int len = 0;<a name="line.84"></a>
<span class="sourceLineNo">085</span>        boolean flipflop = false;<a name="line.85"></a>
<span class="sourceLineNo">086</span>        int prevNibble = 0;<a name="line.86"></a>
<span class="sourceLineNo">087</span>        final int limit = text.length();<a name="line.87"></a>
<span class="sourceLineNo">088</span>        for (int pos = 0; pos &lt; limit; pos++) {<a name="line.88"></a>
<span class="sourceLineNo">089</span>            char ch = text.charAt(pos);<a name="line.89"></a>
<span class="sourceLineNo">090</span>            if (Character.isWhitespace(ch))<a name="line.90"></a>
<span class="sourceLineNo">091</span>                continue;<a name="line.91"></a>
<span class="sourceLineNo">092</span>            int nibble = Character.digit(ch, 16);<a name="line.92"></a>
<span class="sourceLineNo">093</span>            if (nibble == -1)<a name="line.93"></a>
<span class="sourceLineNo">094</span>                throw new IllegalArgumentException("invalid character '" + ch + "' in byte array");<a name="line.94"></a>
<span class="sourceLineNo">095</span>            if (flipflop)<a name="line.95"></a>
<span class="sourceLineNo">096</span>                array[len++] = (byte)((prevNibble &lt;&lt; 4) | nibble);<a name="line.96"></a>
<span class="sourceLineNo">097</span>            else<a name="line.97"></a>
<span class="sourceLineNo">098</span>                prevNibble = nibble;<a name="line.98"></a>
<span class="sourceLineNo">099</span><a name="line.99"></a>
<span class="sourceLineNo">100</span>            // bitwise inversion of boolean<a name="line.100"></a>
<span class="sourceLineNo">101</span>            flipflop ^= true;<a name="line.101"></a>
<span class="sourceLineNo">102</span>        }<a name="line.102"></a>
<span class="sourceLineNo">103</span>        if (flipflop)<a name="line.103"></a>
<span class="sourceLineNo">104</span>            throw new IllegalArgumentException("byte array has an odd number of digits");<a name="line.104"></a>
<span class="sourceLineNo">105</span><a name="line.105"></a>
<span class="sourceLineNo">106</span>        // Account for any squeezed-out whitespace<a name="line.106"></a>
<span class="sourceLineNo">107</span>        if (len &lt; array.length) {<a name="line.107"></a>
<span class="sourceLineNo">108</span>            byte[] temp = new byte[len];<a name="line.108"></a>
<span class="sourceLineNo">109</span>            System.arraycopy(array, 0, temp, 0, len);<a name="line.109"></a>
<span class="sourceLineNo">110</span>            array = temp;<a name="line.110"></a>
<span class="sourceLineNo">111</span>        }<a name="line.111"></a>
<span class="sourceLineNo">112</span><a name="line.112"></a>
<span class="sourceLineNo">113</span>        // Done<a name="line.113"></a>
<span class="sourceLineNo">114</span>        return array;<a name="line.114"></a>
<span class="sourceLineNo">115</span>    }<a name="line.115"></a>
<span class="sourceLineNo">116</span>}<a name="line.116"></a>
<span class="sourceLineNo">117</span><a name="line.117"></a>




























































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